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Abstract
Block caving is an underground mining method of great importance to the future extraction of suitable, large, low-grade deposits due to high production rate potential and low operating cost. Block caving success relies on cave propagation, which is governed by the caving geomechanics operating at a location in space and time. Knowledge of caving geomechanics is evolving and there are significant safety and economic risks from irregular propagation. Understanding caving geomechanics is further complicated as we are forced into deeper, stronger rockmasses, with higher stresses. Discrete geological structures (e.g. faults) can also affect cave propagation; however, little is known about the how, when and where of this influence. There is a need for enhanced knowledge of caving geomechanics and the effects of discrete geological structures on cave propagation for improved block cave management. This thesis aims to further the understanding of caving geomechanics.
Multiple factors affect block caving, making understanding the process for optimisation a challenge. This thesis uses a systems approach coupled with virtual reality scientific visualisation as a tool to integrate data from the block cave mining system to understand interrelationships. This approach improves the understanding of rockmass response with new concepts developed from observations.
Explaining remotely triggered seismicity is challenging. An appreciation of time in seismic analysis enables effective cause and effect examination. This thesis develops the seismic space-time sequence concept to explain: near cave, discrete geological structure related and remotely triggered seismicity. Process maps are used to identify the likely factor(s) driving damage. The concept of a critical state of instability, linked to damage process theories, relates stress change to severity of damage and space-time rockmass response. These approaches enable understanding between: induced stress, micro damage, macro damage accumulation and seismicity. This leads to the space-time identification of: cave geometry-driven, fault-driven and geological contact-driven damage.
These techniques have immediate implications for block caving operations to better understand the caving geomechanics, improving management of these caves. The approach is attractive to the block caving industry and is being applied at an operation upon request. Future work will improve the method toward real-time management of block caves.